In recent years, electric vehicles or hybrid cars have accommodated attention as eco-friendly motor vehicles instead of vehicles using a gasoline engine or a diesel engine. However, the electric vehicles or hybrid cars require a power source with high voltage and high output, so that multiple batteries are connected in series.
Therefore, a battery voltage monitor for always monitoring whether a terminal voltage of each of the batteries is maintained at a predetermined value is required in order to obtain the high voltage from the batteries. However, work of connection between multiple battery terminals and voltage detecting terminals and work of assembly of the voltage detecting terminals and a printed circuit have been troublesome until now.
<Voltage Detection Principle of Battery Voltage Monitor Handled by the Invention>
First, a voltage detection principle of a battery voltage monitor handled by the invention will be described.
<<Arrangement of Plural Batteries>>
FIG. 5 is a connection circuit diagram of batteries which the battery voltage monitor according to the invention targets for monitoring. In FIG. 5, each of the batteries B1 to Bn is one battery constructing the minimum unit, and includes a positive electrode post 10P and a negative electrode post 10N. Both of the positive electrode post 10P and the negative electrode post 10N have the same shape and are formed in a columnar shape and are bolts whose surfaces are grooved. The battery B2 adjacent to the battery B1 similarly includes a positive electrode post 10P and a negative electrode post 10N, but the arrangement is set in an opposite direction and the negative electrode post 10N of the battery B2 is placed next to the positive electrode post 10P of the battery B1 and the positive electrode post 10P of the battery B2 is placed next to the negative electrode post 10N of the battery B1. Further, the battery B3 adjacent to the battery B2 similarly includes a positive electrode post 10P and a negative electrode post 10N, but the arrangement is set in a direction opposite to the battery B2 and the negative electrode post 10N of the battery B2 is placed next to the positive electrode post 10P of the battery B3 and the positive electrode post 10P of the battery B2 is placed next to the negative electrode post 10N of the battery B3. Afterward, based on this rule, the batteries are arranged in like manner and an A-line battery of a battery pack made of the batteries B1 to Bn is completed.
In like manner, a B-line battery is also formed.
<<Series Connection of Batteries B1 to Bn>>
In FIG. 5, the positive electrode post 10P of the battery B1 is connected to the negative electrode post 10N of the adjacent battery B2 by a busbar 10. The busbar 10 is made by punching a conductive metal plate in a rectangular shape and insertion holes for inserting the electrode posts are opened in two places. The positive electrode post 10P of the battery B1 is electrically connected to the negative electrode post 10N of the battery B2 by respectively inserting the positive electrode post 10P of the battery B1 and the negative electrode post 10N of the adjacent battery B2 into the two insertion holes of this busbar 10 and respectively tightening the electrode posts with nuts. Afterward, this is sequentially repeated and a positive electrode post 10P of the last battery Bn of the A-line battery is connected to a negative electrode post 10N of the last battery Bn of the B-line battery through a long busbar 10AB and afterward, connections between an electrode post of the battery and an electrode post of the adjacent battery through a busbar 10 are repeated inside the B-line battery in like manner and finally, a series connection circuit of all the batteries of the A-line battery and the B-line battery is completed, and a DC high-voltage power source using a terminal 10T1 as a negative electrode and a terminal 10T2 as a positive electrode is formed.
<<Formation of Battery Voltage Monitoring Circuit>>
In order to monitor whether terminal voltages of all the batteries of the A-line battery and the B-line battery of FIG. 5 are maintained at a predetermined voltage, a battery voltage monitor 60 as shown in FIG. 6 is added to a DC high-voltage circuit of FIG. 5. FIG. 6 is a circuit diagram of a battery circuit apparatus made by electrically connecting terminals 50 for voltage detection to the busbars 10. As the electrical connection, welding, solder, elastic pressure welding (see Patent Literature 1 as the elastic pressure welding), etc. are used. A detection line 40W is laid from each of the terminals 50 for voltage detection electrically connected in this manner to each of the terminals of the battery voltage monitor 60. In the case of assuming that the terminals of the battery voltage monitor 60 connected to terminals of the busbars 10 of the lower side of the A-line battery in FIG. 6 are set at T1, T3, T5, . . . , Tn-1 sequentially from the batteries near to the battery voltage monitor 60 and the terminals of the battery voltage monitor 60 connected to terminals of the busbars 10″ of the upper side of the A-line battery in FIG. 6 are similarly set at T0, T2, T4, . . . , Tn sequentially from the batteries near to the battery voltage monitor 60, a closed circuit is formed by sandwiching a DC voltmeter between both the electrode posts of the battery B2 when a negative terminal Pn of the DC voltmeter is connected to the terminal TO and a positive terminal Pp is connected to the terminal T1 in order to measure a terminal voltage of the battery B1, so that a DC voltage between both the electrode posts of the battery B2 is obtained by reading a scale of the DC voltmeter.
Similarly, in order to measure a terminal voltage of the battery B2, the negative terminal Pn of the DC voltmeter could be connected to the terminal T2 and the positive terminal Pp could be still connected to the terminal T1.
Similarly, in order to measure a terminal voltage of the battery Bn, the negative terminal Pn of the DC voltmeter could be connected to the terminal Tn and the positive terminal Pp could be connected to the terminal Tn-1.
The above is a method for measuring the terminal voltages of the A-line battery.
Wiring of the battery voltage monitor 60 is not illustrated in the B-line battery side, but terminal voltages of the B-line battery side could be measured in a manner similar to the above.
<Improvement to Voltage Monitor (FIG. 6) in Patent Literature 1>
FIG. 7 is a front view describing a state of connection between a terminal 50 for voltage detection and both electrode posts (a positive electrode post 10P and a negative electrode post 10N) of a battery of a voltage monitor described in Patent Literature 1. In FIG. 7, in the voltage monitor described in Patent Literature 1, the terminals 50 for voltage detection erected and connected, in welding regions F1, to busbars 10 between batteries for connecting plural batteries B1 to B6 constructing an A-line battery of an electric vehicle in series are inserted into through holes 40L provided in a printed board 40 and are connected to a wiring pattern provided on this printed board 40 by soldering. The terminal 50 for voltage detection is formed using a thin metal plate in order to give a flexible structure capable of cushioning an external force in the case of applying the external force so that a crack etc. do not occur in a solder portion which is a place of connection between the printed board 40 and the terminal 50 for voltage detection.
However, the terminal 50 for voltage detection had a problem that it is difficult to position the terminal 50 for voltage detection in the case of inserting the terminal 50 for voltage detection into the through hole 40L since the terminal 50 for voltage detection has low rigidity due to flexible design and flexes under the own weight of the terminal 50 for voltage detection.
Also, all the batteries are provided with the terminals 50 for voltage detection one by one, but as described above, it was difficult to position the terminals 50 for voltage detection with the through holes 40L, so that it was extremely difficult to collectively insert the plural terminals 50 for voltage detection into the respective through holes 40L. As a result, work of attaching the terminals 50 for voltage detection to the printed board 40 had a problem that each of the terminals 50 for voltage detection must be inserted into each of the through holes 40L one by one and long labor time is required.
Also, since the terminal 50 for voltage detection is separate from the busbar 10, a work process of welding, solder, elastic pressure welding, etc. for connecting both of the terminal 50 and the busbar 10 was required, so that productivity was low.
Hence, the present applicant focuses attention on the problems described above, and previously invented a busbar for battery electrode post connection with high productivity capable of easily attaching the terminals for voltage detection to the printed board, and applied for a patent (Patent Literature 2).